The present invention relates to devices which allow an optical signal to be modulated on the basis of an electrical signal. Such devices are most often integrated on the surface of a substrate consisting of a material whose optical properties change under the influence of an electric field which is applied to it. These devices make it possible in particular to modulate a light signal in order to make it possible to transmit analogue signals, for example vestigial side band amplitude -modulated (VSBAM) television signals over cabled television networks employing optical fibres. In order to enhance the linearization of the electrooptical response of an integrated optical modulator, the applicant has filed a French Patent Application under No. 2 670 589. This invention is based on the simultaneous modulation of two distinct regions of a Y-junction coupler. The modulation of a "coupler"-type region has the drawback of not being very effective, since it necessitates a two-conductor electrode structure and thus a vertical electric field (on Z-cut LiNbO.sub.3).